Malodour counteracting compositions

ABSTRACT

A malodour-counteracting composition containing 
     (i) a salt of general formula (I) 
       R 1 R 2 R 3 R 4 N + X −   (I)
 
     wherein R 1 , R 2 , R 3 , R 4  are independently selected from C 1-4  alkyl, or R 1 , R 2 , R 3 , R 4  may together constitute a nitrogen-containing cyclic system in which the nitrogen is part of a pyridinium or an imidazolinium ring; and X −  is a counterion characterised by its protonated form having an acidity constant (pKa) lying between 1 and 6; and
 
(ii) an alpha, beta-unsaturated carbonyl compound of the general formula
 
       R 5 R 6 C═CR 7 C(═O)YR 8   (II)
 
     wherein R 5 , R 6 , R 7  and R 8  are independently selected from hydrogen and C 1-10  hydrocarbyl residues which may be saturated, unsaturated, aromatic, cyclic, branched or unbranched, and are optionally substituted, or R 5 , R 6 , R 7  and R 8  may together constitute a cyclic system and Y is oxygen or a single covalent bond, with the proviso that Y is a covalent bond when R 8  is hydrogen. The composition may be incorporated into consumer products and is able to remove malodours from the air or from surfaces.

This disclosure relates to malodour counteracting compositions, to methods of using these compositions and to perfumes incorporating them.

The problem of malodours has been with mankind for as long as civilization. There are very few articles or things which do not have some odour associated with them. Often this odour is undesirable, such as tobacco smoke odour, cooking odours, and odours of, e.g. mould, bathroom and pets. The compounds that cause malodour are often highly volatile, and are encountered in the air, as well as on substrates such as fabric, hard surfaces, skin and hair.

Many fragrance compositions merely mask undesirable odours with a stronger, desirable odour. The malodorant molecules survive the presence of perfume.

There are several routes to reducing malodour, for example by using absorbers, such as sodium bicarbonate, activated charcoal, zinc ricinoleate, zeolites, cyclodextrins, etc. These compositions are only partially effective and they have the disadvantage of removing both malodour and fragrance

Other approaches to reducing malodour that have been proposed include chemical neutralization, reducing or eliminating the partial vapor pressure of the malodour in air.

While all of the approaches set forth above are designed to mitigate malodors, none of them are free from defects, such as inadequate elimination of the malodor, or taking too long to provide a malodour benefit, leading to unacceptable performance.

It has now been found that the addition of specific quaternary ammonium salts to alpha, beta-unsaturated esters, aldehydes and ketones may significantly improve their ability to remove malodour from the air. There is therefore provided a malodour-counteracting composition comprising

(i) a salt of general formula (I)

R₁R₂R₃R₄N⁺X⁻  (I)

wherein R₁, R₂, R₃, R₄ are independently selected from C₁₋₄ alkyl, or R₁, R₂, R₃, R₄ may together constitute a nitrogen-containing cyclic system in which the nitrogen is part of a pyridinium or an imidazolinium ring; and X⁻ is a counterion characterised by its protonated form having an acidity constant (pKa) lying between 1 and 6; and

(ii) an alpha, beta-unsaturated carbonyl compound of the general formula

R₅R₆C═CR₇C(═O)YR₈  (II)

wherein R₅, R_(6,) R₇ and R₈ are independently selected from hydrogen and C₁₋₁₀ hydrocarbyl residues which may be saturated, unsaturated, aromatic, cyclic, branched or unbranched, and are optionally substituted, or R₅, R₆, R₇ and R₈ may together constitute a cyclic system and Y is oxygen or a single covalent bond, with the proviso that Y is a covalent bond when R₈ is hydrogen.

There is additionally provided a method of counteracting malodour in the atmosphere or on a substrate, comprising the application to the atmosphere or substrate of a composition as hereinabove described.

Non-limiting examples of compounds according to the formula I (hereinafter “Compound I”) include tetrabutylammonium acetate (CAS No: 10534-59-5) and tetraethylammonium benzoate (CAS No: 16909-22-1). The acidity constant (pKa) of the protonated counterion is particularly between 2 and 5, more particularly between 3 and 5.

The optional substituents of the compound of Formula II (hereinafter “Compound II”) include hydroxy, alkoxy, keto, alkoxycarbonyl, carbalkoxy and ether

Particular embodiments of Compound II are those wherein

-   -   (a) R₂ is hydrogen and Y is absent; and     -   (b) at least one of R₅ and R₆ is an ester group and Y is an         oxygen atom, such that the compound is a di-ester or tri-ester.

Non-limiting examples of Compound II include citral, cinnamaldehyde and damascone.

The weight ratio of Compound Ito Compound II advantageously lies within the range 1:1000 to 1:5, particularly between 1:500 to1:20, and more particularly 1:300 to 1:30.

The malodour-counteracting compositions may also contain other adjuncts known in the art, for example solvents such as glycols and glycol ethers, preservatives such as parabens, such as methyl paraben, propyl paraben, butyl paraben, ethyl paraben, isopropyl paraben, isobutyl paraben, benzyl paraben, and their salts; alcohols, such as benzyl alcohol, phenyl ethyl alcohol; boric acid; 2,4,4′-trichloro-2-hydroxy-diphenyl ether; phenolic compounds, such as phenol, 2-methyl phenol, 4-ethyl phenol; organic acids, such as sorbic acid, benzoic acid, and their salts; anti-oxidants and/or UV screens such as pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 2,6-di(ter.butyl)-4-methylphenol, 2-ethylhexyl para-methoxycinnamate; stabilizers/chelants such as ethylenediaminetetracetates, pentetic acid, etidronic acid, diethylenetriaminepentaacetates, and ethylenediamine disuccinate.

One embodiment of the disclosure comprises malodour-absorbing perfume containing at least 0.075% w/w of at least one Compound II, together with at least one Compound I, Compound I being selected such that its solubility in the perfume is at least 100 ppm by weight at 25° C., particularly at least 200 ppm. In a further particular embodiment, there is present in the perfume at least 0.1% w/w, particularly 0.25% w/w, more particularly 0.5%.w/w, more particularly 2% w/w, based on the perfume of at least one Compound II.

For the purposes of this application, a perfume is regarded as a mixture of odiferous perfume ingredients as described in standard texts such as “Perfume and Flavour Materials”, by Steffen Arctander (Montclair, N.J., 1969) published in two volumes, “Perfume and Flavor Materials of Natural Origin”, S. Arctander (Elizabeth, N.J., 1960), together with solvents such as diethyl phthalate, dipropylene glycol, isopropyl myristate, triethyl citrate, and glycol ethers such as carbitol, and those sold under the ‘Dowanol’ brand (e.g. Dowanol DPM, Dowanol TPM, Dowanol DPnP, Dowanol DPMA etc.). In general the water content of a perfume is usually below 1%, more typically under 0.3%, and often below 0.1%, and this tends to limit dramatically the solubility of salts within perfume.

In a particular low-odour embodiment, Compound II comprises a fumarate (i.e. a di-ester of trans-butane-1,4-dioic acid). Certain fumarates such as dihexyl fumarate are known as counteractants of nucleophilic malodorants, for example amines and thiols (U.S. Pat. No. 6,610,648 and U.S. Pat. No. 3,077,457). It has been found that a combination with Compound I with such a fumarate has a significantly enhanced malodour reduction capability, in some cases an order of magnitude better than known compositions. A particular combination is a mixture of at least one of tetrabutylammonium acetate and tetraethylammonium benzoate with dihexyl fumarate in a ratio of from 1:300 to 1:30

Another aspect of the disclosure concerns a method for removing malodour from the air, comprising treatment of the air directly or indirectly, the latter via the treatment of a substrate such as a hard surface, fabric, hair or skin in contact with the air, comprising the exposure to the air or the application to a substrate of a consumer product incorporating an effective amount of a malodour-counteracting composition as hereinabove defined. The malodour-counteracting composition may be added directly into the consumer product or incorporated via a perfume as described herein.

The compositions of the present invention may be incorporated into various products, e.g., consumer products, such as for example the products set forth in more detail below. There is therefore also provided a consumer product, comprising a consumer product base and an effective amount of a malodour-counteracting composition as hereinabove described.

As used herein, “consumer products” include, for example products designed for personal care, as well as more functional products directed towards fabrics, hard surfaces, toilets, and air fresheners. Suitable products applied to the skin may include, for example, talcum powder, deodorants and antiperspirants in the form of sprays, soft solids, and solids, lotions, and oils, and soap, syndet, and combination soap and syndet personal wash bars, personal wash liquids, and personal wipes. Products for the hair encompass for example, shampoos, conditioners, styling sprays, mousses, gels, hair wipes, hair sprays, and hair pomades. Household products include fabric washing liquids and powders, fabric conditioners, wipes, dishwashing liquids and powders, hard surface cleaning liquids and powders, and aqueous and non-aqueous sprays. The term ‘air fresheners’ may include, for example, sprays, candles, gels, plug-in electrical devices, battery-operated and other forms of vapour dispensing devices for introducing compositions into spaces, and liquid wicking systems.

By “consumer product base” is meant the totality of all of the ingredients needed to prepare a consumer product, apart from the malodour-counteracting composition. These will naturally vary depending on the nature of the composition, but they are no different in kind and proportion from those known and used in the art.

As used herein, an “effective amount” of the composition, e.g., consumer product, will vary depending upon the intended use, the composition used, the ambient conditions, and other well known variables. Using the examples provided below, one skilled in the art may judge the appropriate amounts of the malodour reducing compositions to be used in order to dispense an effective amount of, e.g. the consumer product, into the space. The table below summarises the amounts of compounds I and II which are suitable for a representative range of consumer products.

Typical Concentration Ranges % Product Perfume Compound I Compound II Air freshener (aerosol)  0.3-1.5 0.0001-0.002 0.003-0.15 Air Freshener (liquid to 100*  0.002-0.1  0.5-5 electrical) Liquid rim-block (toilet care)   2-10 0.0002-0.05 0.025-2 Fragranced candles   1-10 0.0001-0.002  0.01-0.1 Hard surface cleaners  0.2-1 0.0003-0.002 0.002-0.1 Underarm deodorants  0.5-3 0.0001-0.001  0.01-0.1 Fabric conditioners 0.25-1.5 0.0005-0.005  0.02-0.15 *A “liquid electrical” is a device that releases fragrance into an atmosphere with the aid of electrical heating. The fragrances generally contain variable proportions of solvent. The 100% perfume figure includes these.

The disclosure is now further described with reference to the following non-limiting examples, which depict particular embodiments.

EXAMPLE 1 Synthesis of dihexyl 2-(propylsulfanyl)succinate (A1)

A reference sample of the 1,4-adduct A1 generated between dihexyl fumarate (DHF) and propanethiol was prepared as follows.

Lithium carbonate (100mg, 1.35 mmol), dihexyl fumarate (0.5g, 1.76 mmol) and ethanol (4.5 g, 5.7 mL) were placed into a round bottom flask along with a magnetic stirrer bar and sealed. Propanethiol (180 μL, 2.0 mmol) was added to the suspension and the progress of the reaction was monitored by gas chromatography using aliquots of the reaction mixture (10 μL) diluted in ethyl acetate (1 mL). After the reaction had reached equilibrium the suspension was filtered (0.2 μm) and the resulting solution was reduced using a rotary evaporator (yield of Adduct A1 ca.100%). NMR and mass spectroscopic analyses confirmed the presence of the desired adduct.

EXAMPLE 2 Effect of Tetrabutylammonium Acetate on the Reaction Between Dihexyl Fumarate (DHF) and Propanethiol

Propanethiol volatile malodorant typical of many mercaptans found in nature, and is conveniently monitored by gas chromatography.

Propanethiol (100 microlitre) was added to a dilution (9%) of dihexyl fumarate in one of two commercial perfumes (ca. 0.6 g in total) at 22° C. and the system left undisturbed for 15 minutes. An aliquot was removed and diluted in ethyl acetate prior to analysis by gas chromatography, and the extent of adduct formation was measured (as a percentage). The experiment was repeated with small amounts (0.2% w/w) of the salt tetrabutylammonium acetate (TBAA) present.

After 15 minutes no adduct was detectable in the absence of the salt. The results shown in Table 1 indicate that TBAA greatly increases the formation of the DHF-thiol adduct even when diluted extensively in perfume.

Other quaternary ammonium salts with counterions from stronger acids (pKa<1) such as Tetrabutylammonium methosulfate, tetrabutylammonium bromide and tetramethylammonium bromide gave no detectable product after the 15 minutes incubation.

TABLE 1 Formation of Adduct A1 in the liquid phase % Reaction Progress Sample TBAA % Perfume (after 15 min) 1 0 1 0.0% 2 0.2 1 6.3% 3 0 2 0.0% 4 0.2 2 4.7%

EXAMPLE 3 Effect of Tetrabutylammonium Acetate (TBAA) on the Scavenging of Propanethiol from Air by Dihexyl Fumarate (DHF)

The ability of dihexyl fumarate to remove thiol from the air in contact with a liquid phase sample was assessed by standard headspace gas chromatography (HGC). Liquid samples (0.5 g) were placed in headspace vials (of volume 20 mL) which were sealed using magnetic caps fitted with PTFE septa. Hexadecane (a chemically inert liquid) was used as a control. It is anticipated that the only mechanism removing thiol from the headspace above hexadecane samples is physical solubilisation. A gas phase malodour challenge (propanethiol, 1 ml of saturated vapour above neat propanethiol at 30° C.) was injected automatically (via a Gerstel MPS 2XL autosampler fitted to an HP 7890 gas chromatograph) into each vial which was then incubated (with agitation) at 40° C. for 30 minutes. Removal of propanethiol from the headspace (scavenging) was measured using headspace gas chromatography. The results were expressed in terms of headspace reduction (HSR) compared to that of hexadecane, as indicated in the following equation:

${HSR} = \frac{\left( {{{control}\mspace{14mu} {malodour}\mspace{14mu} {peak}\mspace{14mu} {area}} - {{sample}\mspace{14mu} {malodour}\mspace{14mu} {peak}\mspace{14mu} {area}}} \right)}{\left( {{control}\mspace{14mu} {malodour}\mspace{14mu} {peak}\mspace{14mu} {area}} \right)}$

The HSRs are shown in Table 2.

TABLE 2 Headspace reduction of Propanethiol by systems comprising 90% dihexyl fumarate together with quaternary salt TBAA (0.01% or 0.1% w/w) and solvent (balance). Sample No. Salt Salt Conc. Solvent RSD Reduction 1 none — — <10% 20% 2 TBAA 0.01% DDPM 10% 33% 3 TBAA 0.01% BA 5% 37% 4 TBAA 0.10% MMB 6% 97% 5 TBAA 0.01% MMB 1% 37% 6 TBAA 0.10% EtOH 11% 97% Key: DDPM = Dowanol DPM BA = benzyl alcohol MMB = 3-methoxyl-3-methylbutanol EtOH = ethanol 

1. A malodour-counteracting composition comprising (i) a salt of general formula (I) R₁R₂R₃R₄N⁺X⁻  (I) wherein R₁, R₂, R₃, R₄ are independently selected from C₁₋₄ alkyl, or R₁, R₂ R₃, R₄ together constitute a nitrogen-containing cyclic system in which the nitrogen is part of a pyridinium or an imidazolinium ring; and X⁻ is a counterion characterised by its protonated form having an acidity constant (pKa) lying between 1 and 6; and (ii) an alpha, beta-unsaturated carbonyl compound of the general formula R₅R₆C═CR₇C(═O)YR₈  (II) wherein R₅, R₆, R₇ and R₈ are independently selected from hydrogen and C₁₋₁₀ hydrocarbyl residues which may be saturated, unsaturated, aromatic, cyclic, branched or unbranched, and are optionally substituted, or R₅, R₆, R₇ and R₈ may together constitute a cyclic system and Y is oxygen or a single covalent bond, with the proviso that Y is a covalent bond when R₈ is hydrogen.
 2. The composition according to claim 1, in which the pKa of the salt of the general formula (I) is between 2 and
 5. 3. The composition according to claim 2, in which the salt is selected from tetrabutylammonium acetate and tetraethylammonium benzoate.
 4. The composition according to claim 2, in which the optional substituents of the compound of formula II are selected from hydroxy, alkoxy, keto, alkoxycarbonyl, carbalkoxy and ether.
 5. The composition according to claim 1, in which the compound of formula II is one in which (a) R₇ is hydrogen and Y is absent; and (b) at least one of R₅ and R₆ is an ester group and Y is an oxygen atom, such that the compound is a di-ester or tri-ester.
 6. The composition according to claim 5, in which the compound of the formula II is selected from citral, cinnamaldehyde, damascene and a fumarate.
 7. The composition according to claim 5, in which the compound of formula II comprises dihexyl fumarate.
 8. A malodour-absorbing perfume containing at least 0.075% w/w, based on the perfume, of at least one compound of formula II, together with at least one compound of formula I, the compound of formula I being selected such that its solubility in the perfume is at least 100 ppm by weight at 25° C., wherein formula (I) is R₁R₂R₃R₄N⁺X⁻  (I) wherein R₁, R₂, R₃, R₄ are independently selected from C₁₋₄ alkyl, or R₁, R₂, R₃, R₄ together constitute a nitrogen-containing cyclic system in which the nitrogen is part of a pyridinium or an imidazolinium ring; and X⁻ is a counterion characterised by its protonated form having an acidity constant (pKa) lying between 1 and 6; and formula II is R₅R₆C═CR₇C(═O)YR₈  (II) wherein R₅, R₆ R₇ and R₈ are independently selected from hydrogen and C₁₋₁₀ hydrocarbyl residues which may be saturated, unsaturated, aromatic, cyclic, branched or unbranched, and are optionally substituted, or R₅, R₆, R₇ and R₈ together constitute a cyclic system and Y is oxygen or a single covalent bond, with the proviso that Y is a covalent bond when R₈ is hydrogen.
 9. The composition according to claim 1, in which the weight ratio of the compound of formula Ito that of formula II is from 1:1000 to 1:5.
 10. The composition according to claim 9, in which the compound of formula I is at least one of tetrabutylammonium acetate and tetraethylammonium benzoate and the compound of formula II is dihexyl fumarate in a ratio of from 1:300 to 1:30.
 11. A method of counteracting malodour in the atmosphere or on a substrate, comprising the application to the atmosphere or substrate of a composition comprising (i) a salt of general formula (I) R₂R₃R₄N⁺X⁻  (I) wherein R₁, R₂, R₃, R₄ are independently selected from C₁₋₄ alkyl, or R₁, R₂, R₃, R₄ together constitute a nitrogen-containing cyclic system in which the nitrogen is part of a pyridinium or an imidazolinium ring; and X⁻ is a counterion characterised by its protonated form having an acidity constant (pKa) lying between 1 and 6; and (ii) an alpha, beta-unsaturated carbonyl compound of the general formula R₅R₆C═CR₇C(═O)YR₈  (II) wherein R₅, R₆, R₇ and R₈ are independently selected from hydrogen and C₁₋₁₀ hydrocarbyl residues which may be saturated, unsaturated, aromatic, cyclic, branched or unbranched, and are optionally substituted, or R₅, R₆, R₇ and R₈ together constitute a cyclic system and Y is oxygen or a single covalent bond, with the proviso that Y is a covalent bond when R₈ is hydrogen.
 12. A method for removing malodour from the air, comprising treatment of the air directly or indirectly, the latter via the treatment of a substrate such as a hard surface, fabric, hair or skin in contact with the air, comprising the exposure to the air or the application to a substrate of a consumer product incorporating an effective amount of a malodour-counteracting composition according to claim
 1. 13. A consumer product, comprising a consumer product base and an effective amount of a malodour-counteracting composition according to claim
 1. 14. A composition according to claim 1, in which the pKa of the salt of the general formula (I) is between 3 and
 5. 15. The composition according to claim 1, in which the weight ratio of the compound of formula Ito that of formula II is between 1:500 to 1:20.
 16. The composition according to claim 1, in which the weight ratio of the compound of formula Ito that of formula II is 1:300 to 1:30.
 17. The perfume of claim 8, wherein the solubility in the perfume of the compound of formula I is at least 200 ppm by weight at 25° C.
 18. The perfume of claim 8, containing at least 0.1% w/w, based on the perfume, of at least one compound of formula II. 